My invention relates to marine engines and particularly to inboard and outboard engines having a lower gearcase which normally operates partially submerged in water.
A major source of trouble occuring with such marine engines is the entry of water into the lower gearcase, especially when the engines are operated in salt water. Water leaking into the gearcase mixes with the liquid lubricant within the gearcase and drastically reduces the lubricant's effectiveness. The water also tends to pit the surfaces of the moving metal parts of the power train and these effects eventually cause failure of the power train and costly repair and replacement of damaged parts.
Up to now the only way to guard against damages caused by the entry of water into the lower gearcase of marine engines has been to periodically take the marine engine out of the water, drain the lubricant and thus determine whether or not the lubricant has been contaminated with water. Such procedure conventionally recommended by the manufacturers of most marine engines, is both costly and time consuming. To take a medium sized sport fishing boat out of the water and check the condition of its outboard marine engine, most marinas charge in excess of $100 plus the cost of materials and supplies used.
My invention provides a sight glass or window in the side of the lower gearcase of the marine engine. The presence of even a few cubic centimeters of water mixed into the conventional liquid lubricant contained within the lower gearcase of a small outboard engine will turn the lubricant from its normally dark brown color to a milky-off white.
Thus by use of my invention the boat's owner or operator can look into the sight glass in the side of the gearcase and immediately determine by observing the color of the lubricant within the gearcase whether or not water has leaked into the lower gearcase. My sight glass permits frequent inspection of the interior of the gearcase without cost or removal of the boat from the water. It also permits prompt corrective action to be taken in the event water has entered the gearcase, thus saving expensive repairs or replacement which would have resulted if the water had remained in the gearcase for an extended period of time.
My invention can be installed by the manufacturer of the marine engine or it may be installed by others onto an existing engine which has no sight glass. In the case of an engine manufacturer, I recommend that the lower gearcase housing be cast with a circular hold having a thickness somewhat greater than the usual thickness of the housing in the side of the casing. The outer edge of this hole can then be threaded to accept the window retaining ring of my sight glass assembly.
In the case of marine engine which has no sight glass, it is first necessary to cut a flanged circular hole in the side of the gearcase and to place an internally threaded lock ring inside the gearcase surrounding the cut hole to receive the retaining ring of the sight glass assembly.
My sight glass assembly includes a window retaining ring which is threadedly mounted into the flanged circular hole in the gearcase housing and bonded to the hole preferably by a suitable quick setting epoxy glue to insure a waterproof connection. The window retaining ring contains a axially concentric groove into which is fitted an O-ring of resilient waterproof material. Then a preferably flat circular transparent sight glass is pressed against the O-ring and firmly locked into waterproof connection with the O-ring by a window cover having a central void and an annular flat face which is pressed against the outer edge of the sight glass opposite to the outer edge of the sight glass which is pressed against the O-ring.
The window cover is threadedly joined to the retaining ring and is preferably locked into place by a lock screw threaded into a hole located in the adjoining outer edges of the window retaining ring and the window cover.
I have found that the foregoing sight glass assembly properly installed is absolutely waterproof and tests conducted over several months have resulted in no leakage of water into the engine's gearcase. My sight glass assembly can be installed either by the engine manufacturer or by others on an existing marine engine at a modest cost as compared with the usual cost of a single conventional checking of the condition of the interior of the marine engine's lower gear case which involves taking the boat out of the water and opening up the gearcase to permit visual inspection of the gearcase's lubricant.